Calculation of zakaat

i have assets and cash valued at R200000 for more than a year.within the last year i have increased this by another 100000.how do i calculate my zakaat.i have started a building project costing 150000,which will be payable whithin 3 months,how does this affect my payment of zakaat.when i pay the zakaat for myself and family what intention do i make.can i use the steam bath while fasting.